As the number of schools implementing systemic, schoolwide positive behavior support (PBS) processes expands (nationally, at least 5,000 schools are participating), increasing attention is being paid to the efficacy of implementation. This article describes a case study of the experiences of Florida's Positive Behavior Support Project, which used a systematic process to understand barriers and facilitators to the successful implementation of schoolwide positive behavior support by schools implementing at high and low levels of fidelity, and the degree to which the project could impact barriers and facilitators. Results indicate that schools implementing with low fidelity tend to identify practical, operational barriers, whereas schools implementing with high fidelity struggle with systems issues. Both high-implementing and low-implementing schools identified the same facilitators to implementation; however, they differed in their views of which facilitators the project could impact. Implications for state PBS project activities are discussed, along with suggestions for future data collection and providing a model of data-based decision making at a macro level. (Contains 2 tables and 4 figures.)